Oh lord, deliver us from the Northmen…

The first thing that seems to come up with “Vikings” is the name itself. One should note that the term Viking is actually a Nordic term for the act of going on a raid and was never used to name a particular people. It referred to all Scandinavians and what they did, not who they were. But regardless of what country they were from, if you were from England (one of the easiest places to get to for raiders) they were all called Danes.
The fact that there was a rise of exploration and general unpleasantness by the Northern European tribes around 793-1066 by raiding (sometimes peaceably and other times bloody) the act became synonymous with the people and they’ve been stuck with that name ever since.